The need for mutually isolating such components until just before their use, e.g. because of an instability of their mixture or for better preserving their sterility, has led to the development of syringes with two or more telescoped and relatively slidable constituents such as an outer barrel and a tubular plunger forming respective compartments for these components. Thus, U.S. Pat. No. 3,052,239 describes a disposable hypodermic syringe wherein an elastic valve head has an imperforate wall adapted to be stretched about an apertured piston head of a plunger to seal the interior thereof against the compartment formed in the outer barrel. U.S. Pat. No. 3,489,147 shows a gasket normally closing the compartment of the outer barrel, this gasket being pierceable by a needle on the plunger to establish communication between the plunger compartment and the barrel compartment. According to U.S. Pat. No. 3,680,558, a multicompartment syringe has a valve which can be opened or closed by a slight rotation of a plunger relative to an outer barrel.
In such syringes, or other mixing devices of this general type, the filling of the several compartments with their respective ingredients sometimes becomes a problem. Especially when one of the components of the mixture to be dispensed is a liquid, that liquid will have to be securely retained in its compartment for an extended period while the device is being assembled or while the remaining compartment or compartments are being filled. Often, moreover, another component of the mixture must be quickly sealed in its compartment to prevent prolonged exposure to the atmosphere; this may create additional difficulties of assembly.